Abstract Introduction Hemoglobin Cheverly is a rare mutation of hemoglobin with less than 10 cases described. It is the result of a mutation in which the hemoglobin molecule becomes unstable from a phenylalanine to serine mutation at codon 45. This results in a discrepancy between pulse oximetry and true oxygen levels in the blood. We present a rare case of Hemoglobin Cheverly leading to difficult interpretation of polysomnography. Case We present a 44-year-old man with a past medical history of Hemoglobin Cheverly, OSA, hypertension, and obesity who follows with pulmonology for OSA. Several years prior to presentation in pulmonary clinic he was diagnosed with Hemoglobin Cheverly after presenting to the hospital with hypoxia. SpO2 on pulse oximetry was 80%, but our patient was well appearing and in no respiratory distress. Due to the significant difference in clinical appearance and SpO2, an ABG was obtained which showed a normal PaO2. After other causes such as carbon monoxide poisoning and methemoglobinemia were ruled out, blood smear was sent for electrophoresis to assess for hemoglobin malformations. This resulted in a variant which could not be identified with electrophoresis. Molecular analysis identified a heterozygous substitution of TTT to TCT or phenylalanine to serine at codon 45. The diagnosis of Hemoglobin Cheverly was made at this time. Our patient reported that his father had a similar issue with pulse oximetry. He subsequently underwent polysomnography due to concern for OSA. In-lab sleep testing revealed an AHI of 24, but pulse oximetry was an unreliable indicator of apnea in this test given our patient’s hemoglobin mutation. Discussion Inconsistencies in the comparison between SpO2 and PaO2 occur in a multitude of clinical scenarios including darker skin pigmentation, poor perfusion, carbon monoxide poisoning, and methemoglobinemia. Rarely does this occur in hemoglobin mutations such as Hemoglobin Chevery. While our patient’s scenario is rare, it brings to light that other, more common patient aspects, may interfere with polysomnography. These differences must be recognized in the interpretation of polysomnography as they may lead to false positives or worse, false negatives. Conclusion This case highlights the importance that pulse oximetry cannot always be the sole indicator of apnea in polysomnography. Other indicators such as air flow must be utilized in patients who’s pulse oximetry cannot be relied on. Further studies should be preformed to investigate the prevalence of conditions that interfere with pulse oximetry testing in polysomnography. This abstract is funded by: None
Coleman et al. (Fri,) studied this question.